Hematoporphyrin and hematoporphyrin-derivative photosensitization of mitochondria.

Laser micro-irradiation experiments show that mitochondria are profoundly affected when cells are irradiated with Hp as the photosensitizer. Functional as well as enzymatic studies on isolated mitochondria show that coupling between respiration and oxidative phosphorylation, Ca2+ transport and respiration are successively lost under irradiation in the presence of either Hp or HpD. ATP-driven Ca2+ uptake, which is not impaired under anoxic conditions with HpD alone, is impaired in the absence of oxygen by the synergistic action of HpD and nitroimidazoles.